Measurement Errors in Monitoring Deflections in Piles Using In-Place Inclinometers

In-place inclinometers are used to measure displacements in piles and retaining walls. They consist of an array of displacement sensors connected by gauge rods. If, after installation, a gauge rod is touching the inside edge of an inclinometer casing it will feel displacements of the casing at the point of contact and these displacements will cause the connected sensor to rotate. Displacements are calculated by assuming that adjacent sensors are connected by a straight line and this will not be so if the gauge rod is forced around abend with a point of contact part way along the gauge rod. The measured displacement will therefore be incorrect. This paper examines this problem and provides calibrated measurements to substantiate it.